Heat-resistant fungi are widely distributed throughout nature, and the fungi grow proliferously in agricultural crops such as vegetables and fruits and contaminate foods and drinks made from the agricultural crops. Moreover, the heat-resistant fungi have high heat resistance compared with general other fungi. For example, the heat-resistant fungi may survive and grow proliferously even after a heat sterilization treatment of an acidic drink and may cause mold growth. Therefore, there are concerns about the heat-resistant fungi as important harmful fungi causing severe accidents.
As major heat-resistant fungi causing contamination accidents, which may be detected from foods and drinks after a heat sterilization treatment, heat-resistant fungi belonging to the genera Byssochlamys, Talaromyces, Neosartorya, and Hamigera are known. Compared with other heat-resistant fungi which form ascospores, the fungi belonging to the above-mentioned four genera have very high heat resistance and are likely to survive after heat sterilization. On the other hand, heat-resistant fungi other than the above-mentioned four genera can be killed under usual sterilization conditions and hence are less likely to cause contamination accidents unless sterilization fails. Therefore, to prevent the accidents by such heat-resistant fungi in foods and drinks and raw materials thereof, it is particularly important to detect and discriminate the heat-resistant fungi belonging to the four genera.
Moreover, to perform accident cause investigation and countermeasure in the case of a harmful accident, it is necessary to identify a fungus causing the accident. Therefore, if the heat-resistant fungi of the above-mentioned four genera can be discriminated, the fungus causing the accident can be detected and discriminated more rapidly.
As a conventional method of detecting and discriminating heat-resistant fungi, a method involving culturing a sample in PDA medium or the like and detecting fungi is known. However, in this method, it takes about seven days until colonies are confirmed. Moreover, identification of the species of the fungi is performed based on the morphology of the fungal organ characteristic to each fungus, and hence it is necessary to continue the culture for further seven days until morphological characters appear. Therefore, according to the method, it takes for about 14 days to detect and discriminate heat-resistant fungi. Such method which requires a long period of time to detect and discriminate heat-resistant fungi is not necessarily satisfactory in terms of sanitary management of foods and drinks, freshness keeping of raw materials, and distribution constraint. Therefore, it is required to establish a method of detecting and discriminating heat-resistant fungi more rapidly.
As a method of rapidly detecting and discriminating fungi, detection methods using a polymerase chain reaction (PCR) are known (e.g., see Patent Documents 1 to 4). However, such methods have problems in that it is difficult to detect specific heat-resistant fungi specifically and rapidly.